"We tracked the behaviour of obese and normal participants towards food or non-food images, registering their reaction during a 2015 cross-institutional study.

The results showed a clear difference between the two groups. I was surprised a person's weight could influence automatic processes in their brain, like those that control visual attention," said Dr Bell.

The findings of the study support a mind-boggling idea: weight could have a bearing on information processing of food. "It seems like being overweight affects your cognitive abilities, making you take an extra interest in certain foods," adds Dr Bell.

Feeling hungry even when you are full

The behaviour, however, is not rare at all. We all experience it when we are hungry: you know you can't help looking at a plate of chips when you are starving! But once we have satiated our appetite, this attention bias is gone. The problem, Dr Bell says, is that obese people seem to see food differently. "The thing we are beginning to understand is that obese individuals behave as though they are hungry, even when they are not."

In the 2015 study, led by Dr Bell and colleagues from The Australian National University in Canberra, both obese and normal participants ate until they were full and reported feeling satiated before starting the experiment. Despite this, obese participants continued to experience a bias towards unhealthy food images.

But what is causing this bias? This is a tough question, Dr Bell says, it is hard to know what comes first. Is this hypersensitivity to unhealthy food causing obesity or is obesity causing this cognitive bias? Currently no study has addressed this question. "One way to investigate whether the cognitive bias leads to obesity or obesity leads to the bias is to do a longitudinal study - to see which develops first. But those studies are lengthy and thus, difficult to get funding for." says Dr Bell.

Another way to address this question would be to follow up on people doing diets and see if losing weight also translates into changes of this attention bias, says Dr Bell. "That would at least tell you if the two things (weight and attention bias for food) are tied together in any direct way".

Distract your attention away from unhealthy options

So what can you do about this? Dr Bell is currently working on developing attention-retraining programs, which he hopes will help tackle, this attention bias. He is also developing a mobile app that might help you look away from those unhealthy treats.

In the meantime, if you are obese, there are a few things you can do at home to fight this attention bias, says Dr Bell. "Now that you know about this bias you can work hard on getting yourself distracted by positive information. For instance, when you are in the checkout queue at the shops, it often feels like the junk food has you surrounded. What our research suggests is that you need to work hard not to keep looking back at those temptations. Find a more positive influence to hold your gaze. If you can keep your eyes away from junk food, you can break that automatic cycle".